What is a Readability Score?
A readability score is a numerical measure of how easy or difficult a piece of text is to read and understand. Readability formulas analyze characteristics like sentence length, word length, syllable count, and vocabulary complexity to produce scores that correspond to grade levels or difficulty ratings. These scores were developed by linguists and educators starting in the 1940s to help publishers, educators, and writers match content to their intended audience's reading ability.
The most widely used readability formulas include the Flesch-Kincaid Reading Ease score, which rates text on a 0-100 scale where higher is easier, and the Flesch-Kincaid Grade Level, which maps to U.S. school grades. The Gunning Fog Index estimates the years of formal education needed to understand text on first reading. The Coleman-Liau Index takes a different approach by using character counts instead of syllable counts, making it computationally simpler while still producing reliable results. Each formula weighs different factors, so using multiple indices gives you a more complete picture of your text's readability.
Readability matters more than most writers realize. The average American reads at a 7th-8th grade level. Government agencies like the NIH recommend writing patient materials at a 6th grade level. Major news organizations target 8th-9th grade. Even sophisticated audiences prefer simpler prose -- Harvard Business Review articles typically score at an 11th-12th grade level, well below what their MBA-holding readers could handle. Writing at an appropriate readability level is not about dumbing down content; it is about respecting your reader's time and cognitive load by making your ideas as accessible as possible.